Engine in bits for a rebore-anything else worth doing?

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paul 300358
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Re: Engine in bits for a rebore-anything else worth doing?

Post by paul 300358 »

I had the same problem with my 1098, I ended up tightening the square key with a pipe to give extra leverage. Kept it all we oiled and tapped in with a hammer shaft. Probably not political correct but it worked.
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Well, I followed Philthehill's advice, and somehow managed to get 2,3&4 in, but it took 2½ hours and umptynine attempts. Given up for now, beer needs to be drunk. Urgently.
The problem seems to be that the compressor does not properly grip the oil ring. As soon as the piston slides down far enough for the oil ring to reach the block, it expands and pushes itself between the block and the compressor, even though I'm pushing down on it. Can the ring compressor be ovalled, causing it not to push the oil ring home properly? It's really not easy to apply more pressure to it, there's nothing to hold it, and it just turns.
Is it best to give the piston a single sharp tap to get it in, or lots of small ones?
Belgium on Friday for MoT-going to be a tall order to get it all reassembled in time now. Think we'll be going in the modern.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Well there was only one bottle I could crack open after today's struggles!
IMG_20190518_233931~2.jpg
IMG_20190518_233931~2.jpg (1.43 MiB) Viewed 2030 times
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
don58van
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Re: Engine in bits for a rebore-anything else worth doing?

Post by don58van »

Sorry about your struggles. I'm sure the beer must have helped :wink:

Does the oil ring always sneak out from the same place on the bottom of the compressor? I am wondering if the compressor does not sit perfectly flat on the top of the block (ie perhaps there is some unevenness on the bottom edge). It might need some truing.

Don
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

No, it's pretty even all the way round. I'm making sure the compressor is flat against the block before holding it down, then tapping the piston home. It's like the compressor just can't hold the oil ring firmly enough. I've tried it in all 4cyls, so I don't think it's a problem with the block not being square.
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
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philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

You should not have these problems - the pistons & rings should be easy to fit into the bores.

It may seem a silly question but are you using the piston ring clamp up the right way???????

Looking at your pictures I cannot determine if the clamp is the right way up or not when fitted to the pistons.

The tightening band ratchet is off-set - so if the wrong way up the grip will slacken as it moves through the clamp.

Is the piston ring clamp the correct size for the pistons? I know that it is adjustable but if the wrong size it could be going oval.

Light taps to get the piston down the piston ring clamp and then one sharp tap to get the ring(s) to enter the bore.

You can have the piston ring compressor too tight - it must be tight enough to clamp the rings into the grooves but loose enough to allow the piston/rings to slide down inside the piston ring compressor.

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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

I did wonder whether I was using it the right way up, but I've tried both ways to no effect. I'm using it with the ratchet at the lower end.
I'll try tightening it up then backing off a notch.
I didn't have this problem when I put the pistons back on last time-but they were standard pistons, although new rings of the same type I'm using now.
Could the compressor have become distorted through 3 years of sitting partially unwound on the shelf?
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

Thank you for the reply.

I have never had any problems fitting pistons and rings into the engine bores using the type of clamp you are utilising.

The clamp is suitable for both standard and oversize pistons. I use the same clamp for fitting pistons/rings into 74mm diameter bores without difficulty.

I do use a different type of clamp when fitting pistons and rings to small block 'A' Series engines. Example below.

https://www.ebay.co.uk/itm/Piston-Ring- ... SwH09ZHCZR

My ratchet clamp sits for ages on the shelf waiting to be used and has never shown any sign of distortion.

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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Thanks for your help Phil! I'll just keep trying, maybe a gentle approach will help!
If I don't have any joy I might try one of those motorcycle clamps, looks like it'll do the job. I did think about trying a jubilee clip, but I haven't got one large enough.
Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Just a thought-what about the orientation of the oil ring gap wrt the clamp? Is that a consideration?
cheers N

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philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

The ring orientation is only a consideration as regards the gap relationship to the ring above/below.

The ring gaps should be at least 45 degrees to the ring above/below.

With the wrap round ring clamp it is not so important to get the ring gaps away from the clamp gap as it would be with the motorcycle type clamp.

The clamp is advertised as a motorcycle clamp but I have that type for the small block 'A' Series and the 'B' Series engine for many years and that type has been around for some considerable time.

I would advise against improvisation with a jubilee clip as that increases the risk of a broken ring.

oliver90owner
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Re: Engine in bits for a rebore-anything else worth doing?

Post by oliver90owner »

Have you checked the ring groove depth cf the ring measurement? Doubtless there will be a specification for that, too. I doubt it is wrong, but one never knows, particularly if the components have been sourced from foreign parts...

Like Phil, I have never had trouble with refitting pistons in bores. Started, using screwdrivers, a long time ago (about 55 years), but I would not advise such practice!
Myrtles Man
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Re: Engine in bits for a rebore-anything else worth doing?

Post by Myrtles Man »

I've improvised (successfully!) with cable ties in past rebuilds.
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

oliver90owner wrote: Sun May 19, 2019 3:48 pm Have you checked the ring groove depth cf the ring measurement? Doubtless there will be a specification for that, too. I doubt it is wrong, but one never knows, particularly if the components have been sourced from foreign parts...

Like Phil, I have never had trouble with refitting pistons in bores. Started, using screwdrivers, a long time ago (about 55 years), but I would not advise such practice!
No, I haven't. I bought the pistons and rings as a set from Moss, so I'd hope they're right!
cheers N

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philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

There is no specification given in the Marina/Ital BL wksp man for the depth of piston ring groove.

All I can suggest is that you measure the width of the ring and measure the depth of the piston ring grove and compare the two.

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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Groove measured with a Vernier caliper at 3.82mm, piston ring at 3.2mm. Oil ring not measured, but visibly narrower than the ring depth.

This is what the piston and clamp looks like from above, before tapping it in. Clamp not fully done up, but it'll only go about 1 more click, maybe 2.
IMG_20190519_220401~2.jpg
IMG_20190519_220401~2.jpg (850.26 KiB) Viewed 1947 times
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

That clamp certainly does not look to be concentric around the piston/rings.

You say that you had no problems when using the clamp previously so there is certainly something strange going on now.!

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Re: Engine in bits for a rebore-anything else worth doing?

Post by Bowie69 »

The bore/piston next to that one looks ovalled, or is a figment of the camera?

Is it possible the pistons aren't round, giving clearance issues?

Do you have old, suitably sized pistons to attempt refitting ?
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

philthehill wrote: Sun May 19, 2019 10:22 pm That clamp certainly does not look to be concentric around the piston/rings.

You say that you had no problems when using the clamp previously so there is certainly something strange going on now.!
Which is why I was wondering whether the clamp could become distorted sitting unwound on the shelf!

I'm going to try clamping the clamp to keep it more circular, but that's a job for tomorrow. 🍺 time now, Derail Ale tonight.
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Bowie69 wrote: Sun May 19, 2019 10:35 pm The bore/piston next to that one looks ovalled, or is a figment of the camera?

Is it possible the pistons aren't round, giving clearance issues?

Do you have old, suitably sized pistons to attempt refitting ?
No, it's a trick of the light, and the skewed perspective of the relatively wide angle lens in a mobile phone.

The pistons are brand new, so I'd hope they're not ovalled!

No, I don't have the old pistons, the machine shop kept them after pressing the new ones on for me. I should have asked for one in hindsight, but too late now.

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
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